Attempts have already been made to oxidize .alpha.,.beta.-or .beta.,.gamma.-unsaturated aldehydes or ketones with the aid of a copper compound in the presence of a heterocyclic nitrogen base, which forms a complex compound with the catalyst, and an alkylamine.
.beta.-Isophorone [3,5,5-trimethyl-cyclohex-3-en-1-one] has been oxidized to ketoisophorone [3,5,5-trimethyl-cyclohex-2-en-1,4-dione] for example with the aid of copper (ii) nitrate in the presence of pyridine and triethylamine in a nitrogen atmosphere. However, in this oxidation, by-products are formed to a considerable degree. These by-products including hydroxyisophorone [3,5,5-trimethyl-4-hydroxy-cyclohex-2-en-1-one], the difficulty separable .alpha.-isophorone [3,5,5-trimethyl-cyclohex-2-en-1-one] and dehydrodimers of isophorone. The yield of ketoisophorone which can be isolated by these procedures is very low, namely 30%. Therefore, a procedure is desired whereby the oxidation of .beta.-isophorone to ketoisophorone can be carried out systematically without the formation of undesired by-products and in high yields.